High energy beam welding, such as laser beam or electron beam welding, is used to join one work piece to another work piece by directing a highly focused beam of energy into a joint between the work pieces to heat and fuse them together. One common type of welding joint is a butt joint in which an edge portion of one work piece is placed in abutting fashion generally against an edge portion of another work piece before welding the edges together.
Exact positioning of the welding beam relative to the joint is essential for a high-quality weld, particularly as the welding beam travels along the joint during the welding process. As examples of imprecise positioning, the welding beam may be laterally offset with the joint, at an incorrect angle relative to the joint, or at an incorrect beam width. Imprecise positioning of the welding beam may result in an unsatisfactory weld, and the quality of the weld may impact many aspects of the completed part, including the microstructure, microhardness, tensile properties, formability, fatigue strength, fracture toughness, and the overall value of the joining process.
There have been substantial efforts to develop practical and reliable automated devices for tracking the joint and moving the welding beam along a prescribed path of travel corresponding to the path of the welding joint. One approach for the tracking of the joint to be welded is the use of contacting probes. Such systems generally utilize the physical characteristics of the work pieces and the joint as a mechanical guide for a sliding or rolling mechanism to which the welding gun is linked. These systems, however, often lose contact with the joint, which can interrupt the operation of the tracking device and compromise the weld quality. Accordingly, use of various non-contacting sensors have been attempted to provide more information about the weld joint. A non-contacting sensor, such as an optical imaging sensor, may be able to repeatedly scan the joint to be welded to provide a map of joint geometry. However, optical imaging may be sensitive to the level of ambient light and smoke emitted by the welding process, and subjective evaluations of the visual image to be tracked may also be an issue. An additional problem with many tracking devices includes the difficulty of positioning the sensors at inaccessible portions of the joint.
Accordingly, it is desirable to provide welding systems and methods with more accurate joint tracking and beam positioning. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and this background of the invention.